The present invention relates to an ink jet recording head to be suitably used for a recording apparatus such as a printer or a plotter, and more particularly to an ink jet recording head comprising a case formed of resin which can accommodate a vibrator unit and a channel unit to be bonded to the distal end of the case.
A related ink jet recording head (which will be hereinafter referred to as a recording head) employs such a structure as to have a vibrator unit bonding a piezoelectric vibrator row to a fixation base, a case formed of resin which forms a housing space capable of accommodating the vibrator unit, and a channel unit to be bonded to the distal end portion of the case.
For example, the channel unit includes a nozzle plate having a plurality of nozzle orifices provided in a row, a channel forming substrate provided with an ink channel communicating with the nozzle orifice from a common ink reservoir via a pressure chamber, and an elastic plate for sealing one of the openings of the pressure chamber and the common ink reservoir, and is fabricated by integrating each of the members in a lamination state. The channel forming substrate is fabricated by etching a silicon wafer. A nozzle plate formed of stainless steel (SUS) is bonded to one face of the channel forming substrate, and the elastic plate is bonded to the other face thereof. The elastic plate is constituted by a composite plate member in which a support plate formed of stainless steel, in which a stainless layer is partially removed to form an island portion, is laminated on a resin film, for example.
Moreover, the free end of each piezoelectric vibrator is exposed to the outside of the case through an opening on the distal end side of the housing space. A distal end face of each piezoelectric vibrator is bonded to the island portion formed in the elastic plate. The free end is extendable to deform the elastic plate so that the volume of the pressure chamber is variable. Furthermore, the fixation base of the vibrator unit is formed of stainless steel and is bonded through adhesion to the internal wall face of the case formed of resin.
When a recording head having such a structure is placed for a long time in very, high humid environment the case is swelled. For example, as shown in FIG. 15, a case 1 is wholly swelled with the moisture absorption of the resin constituting the case 1. As shown in FIG. 16, moreover, a channel unit 2 is bonded to the distal end face of the case 1. Since the channel unit 2 has a channel forming substrate formed of silicon and a nozzle plate formed of stainless steel, the swelling is not caused by the moisture absorption. For this reason, the distal end side of the case 1 is constrained by the channel unit 2 so that the amount of deformation is decreased, and the amount of deformation is increased as being distant from the channel unit 2. Accordingly, the proximal end side of the case 1 (that is, the attachment face side opposite to the channel unit 2) is greatly deformed.
Furthermore, since a fixation base 6 of a vibrator unit is also formed of metal such as stainless steel, the swelling is not caused by the moisture absorption. For this reason, the fixation base 6 and the case 1 which are bonded to each other deform due to the moisture absorption similarly to a bimetal phenomenon such that they are curved to be convex toward the outside of the case 1.
As a result, mechanical stress is applied to the bonding interface of a piezoelectric vibrator 3 and an island portion 4 and that of a resin film portion 5 and the island portion 4. More specifically, the fixation base 6 falls down toward the outside of the case 1 together with the case 1 so that the piezoelectric vibrator 3 also falls down. Consequently, mechanical stress is applied to the bonding interface. When the mechanical stress is excessively applied, the bonding interface is separated so that the recording head might be broken.
It is therefore an object of the present invention to enhance the connecting reliability of a piezoelectric vibrator unit.
In order to achieve the above object, according to the present inventions there is provided an ink jet recording head, comprising:
a vibrator unit, in which at least one piezoelectric vibrator is fixed on a base member in a cantilevered manner, such that a first region of the piezoelectric vibrator is fixed on a first face of the base member; and
a resin case, formed with a housing space extending through a first end face to a second end face thereof, the housing space including:
a first housing part, which opens to the first end face of the case, in which a part of the piezoelectric vibrator except for the first region is housed;
a second housing part, which continues to the first housing part, the second housing part defined by a first inner face extending in a first direction which is parallel with an extending direction of the piezoelectric vibrator, on which a first part of a second face of the base member which is opposite to the first face is bonded, and a second inner face extending in a second direction which is perpendicular to the first direction; on which a part of a third face which connects the first face and the first part of the second face is bonded; and
a third housing part, which continues to the second housing part, the third housing part being isolated from a part: of the base member which includes a second part of the second face.
Preferably, the recording head further comprises a channel unit which is provided on the first end face of the case such that free end face of the piezoelectric member is bonded thereon.
In the above configurations, the mechanical linkage of the base member and the case is eliminated in the third housing part, it is prevented the base member from inclining together with the swelling deformation of the resin case due to moisture absorption. Accordingly, it is possible to prevent the piezoelectric vibrator from separated from the base member due to mechanical stress application onto the bonding interface between the piezoelectric vibrator and the base member. As a result, it is possible to enhance the connecting reliability of the piezoelectric vibrator.
Preferably, the first part of the second face of the base member opposes to at least the first region of the piezoelectric vibrator.
In this configuration, it is secured a bonding region necessitately required for receiving reaction force with the motion of the piezoelectric vibrator. Consequently, it is possible to enhance the connecting reliability of the piezoelectric vibrator without damaging the jetting characteristic of ink drops.
Preferably, the second part of the second face of the base member is larger than the first part of the second face of the base member.
In this configuration, the base member can be easily held by a jig for mounting the vibrator unit into the case. Further, heat radiating effect can also be enhanced.
Preferably, inner wall faces of the case defining the third housing part is not bonded to the base member.
Here, it is preferable that the third housing part is defined by a third inner face extending from a boundary of the first part and the second part of the second face of the base member in the second direction, and a fourth inner face extending in the first direction to the second end face of the case.
In the above configurations, a part of the case formed with the third inner wall face acts to restrict the inclination of the base member due to the swelling. Furthermore, the space formed by the third and the fourth inner wall faces can be utilized to arrange components of the recording head in the space or can be utilized as a heat radiating space. Consequently, the degree of freedom for the design of the recording head can be increased.
Further, it is preferable that the recording head further comprises a circuit board mounted on the second end face of the case. An area defined by the third inner wall face is larger than a size of the circuit board.
Still further, it is preferable that a groove for holding ink therein is formed at a boundary of the third inner wall face and the fourth inner wall face.
Preferably, the case includes a flange member extending from the second and face thereof in the second direction. A positioning member is formed on a distal end portion of the flange member, which is abutted on a carriage member on which the recording head is mounted.
Preferably, the recording head further comprises a reinforcing plate member provided on a first part of an outer wall of the case the first part of the outer wall being a part opposing to at least the third housing part.
In this configuration, the swelling of the case due to moisture absorption can be restricted by the base member and the reinforcing plate member sandwiching the case therebetween. Therefore, the inclination of the base member due to the swelling deformation can be prevented more reliably.
Here, it is preferable that the reinforcing plate member extends so as not to extend to the first end face of the case.
Here, it is preferable that the reinforcing plate member extends to a position opposing to the second inner wall face of the case.
In the above configurations, a part of the case which is not covered by the reinforcing plate member is allowed to be swelled. Due to this swelling deformation, it is possible to reliably prevent such a drawback that the channel unit and the vibrator unit are separated in the first direction, thereby the connecting reliability of the piezoelectric vibrator can be enhanced.
Further, it is preferable that a Young""s modulus of the reinforcing plate member is higher than a Young""s modulus of the base member.
In this case, the reinforcing plate can be thinly fabricated so that the size of the recording head can be reduced.
Further, it is preferable that the base member and the reinforcing plate member are made of the same material.
In this case, the material characteristics of the reinforcing plate and the fixation base are equal to each other. Consequently, the easiness of the design can be obtained.
Here, it is preferable that a thickness of the reinforcing plate member is identical with a thickness of the base member.
Further, it is preferable that the reinforcing plate member is made of metal.
Here, it is preferable that the reinforcing plate member is made of stainless steel.
In this case, a necessary rigidity can be obtained while a processing can easily be carried out. Furthermore, it is also possible to efficiently radiate the heat of the recording head through the reinforcing plate. Moreover, there is no moisture permeability. Therefore, it is possible to prevent the swelling deformation of the case due to moisture absorption more reliably.
Preferably, the case is made of thermosetting resin.